This invention relates to new and improved bending and forming apparatus embodiments of which are particularly advantageous for use in up bending or "air" bending procedures and as part of a die assembly incorporated in a press.
The invention will be described in this frame of reference, but only for purposes of illustration and not by way of limitation, either as to its application or the form of its embodiment.
In the use of known tools and systems for bending and forming, it has invariably been found that the material worked has been distorted and undesirably stressed. This affects adversely the quality of the end product. This problem which the present invention solves becomes more readily apparent when considering a representative installation of the prior art in which up bending takes place. See FIG. 1 of the accompanying drawings in this respect. As seen therein, the conventional bending and forming tool is a spring biased anvil device mounted in connection with an upper die plate forming part of the upper half of a die assembly. Its lower half incorporates a spring biased pad in an aligned opposed relation to the anvil. This pad is in a side by side relation with a forming die which together therewith interrelates with the anvil in a bend and form operation as the die assembly is closed in a cyclic operation of the press in which it is embodied. By reason of the bias thereon, the pad provides a surface normally elevated relative to the upper or matrix surface of the lower die plate, reaching to the upper level of the projected operating portion of the forming die. The pad provides a backing over which material to be worked moves to the projected co-planar part of the forming die in establishing its working station. As shown, schematically, the lower die plate will incorporate an additional die or dies, respectively located for a cooperative working relation with a punch or cutting tool or a plurality thereof in connection with and fixed to depend from the upper die plate. As conventionally illustrated, the upper die plate suspends a spring biased stripper plate through which the cutting and/or punching tool or tools must pass on the closing of the die assembly to interact with its or their aligned die in cutting or punching the material being worked. During the closing of the die assembly the stripper plate is biased to be in advance of the working end or ends of the cutting and punching tool or tools and serves to hold the material to be worked so such tools can properly function. For convenience of illustration, in FIG. 1 only a single spring is shown with each of the stripper plate and the pad opposed to the forming anvil. In fact, however, a plurality of springs is applied in each instance, producing a complexity in their choosing and arrangement in efforts to balance the associated apparatus in the course of its function. The installation of such apparatus in a proper relationship has always been very difficult and time consuming.
In the cyclic operation of the press in which the die assembly of FIG. 1 is incorporated, the upper half of the die assembly will move towards a closed position with reference to the lower half in the process of which the spring biased anvil is the first tool to engage the material to be worked. It is desirable that in its first contact the anvil sets the material against the spring biased pad and the co-planar projected portion of the forming die, to condition it and fix its position for the bend and form operation. In the wipe bending procedure schematically illustrated in FIG. 1, it will be seen that as the anvil moves downwardly to initiate the bend, it applies pressure to the material worked in an adjacent but spaced relation to that portion of the forming die which serves as its base. The consequence, seen in FIG. 1, is an inherent and naturally resulting distortion of the material being worked, resisted only in part by the spring biased pad adjacent the forming die. What in fact happens is that irregularities occur in the plane of the material and stress is built therein as the initial bending and forming proceeds. Keep in mind that during this initial bending and forming operation the bias of the anvil in respect to the material worked is opposed by the spring bias on the pad. The interaction is not by any means firm and positive as to control of the material. The stress and distortion embodied in the material worked during the initial bend and form operation (known as "air bending") is built into the end product as the die assembly is brought to a fully closed condition. At such time the cutting and punching tools function and whatever bend and form has been effected is set. The problems of stress and distortion of the material are compounded in the closing procedure by the interaction of the stripper plate, as biased by its backing springs. There are just so many spring forces involved and imposed on the material as the die assembly is closed that full or reasonably full control of the positioning of that portion of the material which is being bent and formed and then set is extremely difficult. There is no positive assurance that the material can be held to maintain that position which is most desirable for achieving the best possible results.
The problems present in the closing of the prior art die assembly such as shown in FIG. 1 are not the sole problems. With spring bias on both the anvil type bending and forming tool and the opposed spring pad, there can be reactant forces acting on the material immediately following the working thereof and the opening of the die assembly.
It is thus clear that the use of a maze of springs to control stock, the working of which includes bending and forming operations, precludes an optimal balance of the forces applied to the material in the working thereof. Not only this, but to get an installation of the springs utilized in a form reasonably suited for the application, there has to be a lot of "cut and try" before an acceptable result occurs.
The foregoing summarizes the state of the prior art and its deficiencies, which create obvious problems the solution of which is urgently required.
The inventors are not aware of any prior art pertinent to the specific improvements of the present invention.